There are numerous methods to detect nitrous oxide gas including calorimetric, chemoluminescent and gas chromotography. However, all these methods require the use of expensive and complex equipment. This makes it impractical to perform real-time monitoring and control of nitrous oxide gas for applications such as medical anesthesia.
The present invention solves these problems by using economical components which are easy to operate and can be readily incorporated into medical anesthetic equipment to detect and control oxygen and nitrous oxide concentration simultaneously.
It has been found that the identity and concentration of a reducing or oxidizing gas species can be determined by electrochemical pumping of oxygen. If one knows the oxygen concentration of a carrier gas containing an unknown reactive species, one can determine the identity and concentration of the unknown species. This is accomplished by applying a voltage across a pair of electrodes separated by a solid electrolyte and "pumping" oxygen through the electrolyte. The voltage required to pump the oxygen is call the pumping voltage. As the oxygen is being pumped, a current flows and this current is measured. This current is called the oxygen limiting current.
It has been found that for many gas species, including methane, hydrogen and propane two oxygen limiting current plateaus are observed as the pumping voltage increases. By measuring these current plateaus one is able to determine the identity and concentration of the reactive gas. However, nitrous oxide does not exhibit this phenomenon, that is, only one current plateau is observed. However, it is possible to determine the nitrous oxide concentration and its identity in the test gas by measuring the oxygen limiting current for two different pumping voltages.